This invention relates to motor control centers, and, more particularly to a motor control center interlock assembly.
Motor control centers in the form of an enclosure containing a motor starter, electric switch and a circuit breaker, such as described in U.S. patent application Ser. No. 09/347,089 entitled Motor Control Center Circuit Breaker Assembly, are interlocked to prevent opening of the enclosure unless the circuit breaker is in the OFF condition. Various interlock arrangements have been employed, U.S. Pat. No. 4,034,169 entitled Electric Switchgear Device with Interlocking Handle Means, describes an interlock operator including a link connecting between the handle of a motor control center and the circuit breaker handle operator to provide interlock function to the motor control center. U.S. Pat. No. 4,448,450 entitled Defeatable Handle and Interlock for Electrical Equipment Enclosure, describes the provision of a through-bolt for holding and releasing a two-part handle from an electrical equipment enclosure. U.S. Pat. No. 4,760,220 entitled Operator Mechanism Having Reduced Handle Throw and Improved Handle Lock, discloses an operator mechanism including a slide bar to prevent withdrawal or insertion of a removable control unit from an electrical equipment enclosure. U.S. Pat. No. 4,806,710 entitled Mechanical Door Interlock for Electrical Equipment Enclosure, describes a door interlock in the form of a drive/latch member carried by the door and a locking member carried by the enclosure to prevent opening of the enclosure door.
A more recent example of an electrical equipment enclosure interlock is described in U.S. Pat. No. 5,019,676 entitled Auxiliary Operator for Circuit Interrupting Apparatus with Interlock between Switch and Housing. A removable control unit of a motor control center is described and has an auxiliary operator handle linked to a circuit breaker handle for control of the circuit breaker externally of the motor control center. An interlock slide bar is driven by the auxiliary handle to an extended position to block removal of the unit when the circuit breaker is in the ON condition.
With the attachment of such interlock assemblies to motor control center doors, there is a need to provide for the tolerance accumulation between the interlock assembly components and the attaching means on the doors. Additionally, considerable installation time is required to position both the interlocks and the means employed to defeat the interlocks when immediate access to the control center is required.